An automotive gear shifter for changing and transmitting the drive torque from prime mover to wheel via multiple change gears by shifting the change gears with a dog clutch comprises a gear train connected with the prime mover side (installed on the input shaft of the gear shifter) and gear train connected with the wheel side (installed on the output shaft of the gear shifter) and changes the speed of the wheel by selectively shifting and connecting the gears of the dog clutches connected with each change gear train (hereinafter simply called the dog clutch) so as to change the gear ratio of the gears of the gear shifter.
There is also available a gear change system in which a bypass transmission path for transmitting driving force is provided and so gear change is operated without interrupting the transmission of the driving force from the input shaft to the output shaft (for example, refer to the Patent Document 1: International Laid-Open Publication WO 01/66971)
Because the gear change according to a prior art is to shift and connect the input shaft side and output shaft side gears of a gear change system by a dog clutch, the gears are disconnected by synchronizing the rotation, that is, controlling the relative rotating speed closer so as to be connected with another. In order to shorten the disconnection time in this operation, it is necessary to disconnect the dog clutch while the connecting force of the dog clutch is still intense.
Because the torque transmission is performed by connecting the gears and engaging the corresponding crests and roots of the gears, connecting them in an opposite phase is preferable but controlling the phase accurately is difficult.
Accordingly, even though the phase has not yet become suitable for the connection, an intense connecting force is applied so as to forcedly connect the gears.
Consequently, an intense driving force is needed for disconnecting and connecting the gears, resulting in excessive size and increased energy consumption of the gear shifter.
In addition, at the time of connecting the gears, because the phase is matched compulsively in a transient state where the transmission of the driving force has just begun, a shock is caused to the body of automobile and uncomfortableness is caused to passengers.
In case of the latter gear change system in which the driving force is transmitted via a bypass transmission path at the time of gear change, the primary driving force transmission path is set open and not in use at time of gear change. Accordingly, load applied to a synchronizing device at the time of gear change decreases to some extent. However, because the rotating speed needs to be increased gradually so that the phase of the dog clutch can be matched, rotational variation must be set small. Consequently, the time needed for gear change becomes longer.
If connecting the gears is made possible by a single attempt of matching the phase, because longer time is needed in matching the phase as explained above, the connecting force of a connection system must be made as large as that of the former gear shifter. Consequently, neither making the gear shifter compact nor decreasing the energy consumption can be realized.